Semiconductor device manufacturing: process – Semiconductor substrate dicing
Reexamination Certificate
2001-11-08
2003-12-02
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Semiconductor substrate dicing
C438S458000, C438S459000, C438S464000, C438S465000
Reexamination Certificate
active
06656820
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device from a step of thinning a semiconductor device substrate to a step of dicing it, and a semiconductor device.
BACKGROUND OF THE INVENTION
Recently, in the field of a semiconductor integrated circuit, developments in making a device more dense and more integrated are progressing and, as a mobile communicating device is getting smaller and lighter, the device is getting finer.
Generally, as an area of a device is getting smaller, the thermal resistance of the device is getting larger. In order to realize a device with a high performance and a high reliability, it is essential to reduce the thermal resistance of the device. Therefore, a variety of approaches have been taken to improve the effect of heat radiation.
The most effective way to reduce the thermal resistance of a device is to thin a whole substrate after an integrated circuit device pattern is formed on the substrate. However, since a GaAs substrate generally used is bristle and is breakable, when a GaAs substrate having a diameter of 3 inches or more is thinned to, for example, 50 &mgr;m or less, a problem occurs that the thinned substrate is broken in subsequent steps of handling, transporting, mounting, and the like.
Generally, in order to prevent a semiconductor substrate from breaking when it is thinned, the substrate is fixed to a supporting plate. A photosensitive adhesive tape having an UV-sensitive adhesive layer is used to fix the semiconductor substrate. Since the UV-sensitive adhesive layer of the UV-sensitive adhesive tape is deteriorated in the adhesion strength by UV irradiation, it becomes easier to remove the thinned substrate from the supporting plate. Further, since no residue remains on the device side of the semiconductor substrate after removing, an UV-sensitive adhesive tape is extensively used.
For example, JP-A 216092/1994 describes a method for fixing a GaAs substrate on a supporting plate by using a tape with a composite structure consisting of a UV-sensitive adhesive layer and a heat foamable adhesive layer. In this method, a semiconductor substrate is fixed on a supporting plate by bonding the UV-sensitive adhesive layer to a surface of the semiconductor substrate on which a device is formed, and by bonding the heat foam able adhesive layer to the supporting plate. After thinning, the adhesion strength of the UV-sensitive adhesion layer is reduced by UV irradiation to remove the thinned semiconductor substrate.
Therefore, in this method, since a thinned substrate is handled in steps of dicing, mounting and the like, a problem remains that the thinned substrate is easy to be broken in handling in these steps.
In addition, JP-A 213662/1997 describes, as a method of preventing a substrate from breaking in the step of thinning the substrate, a method which comprises, first, forming a dicing groove having a predetermined depth on a wafer on which semiconductor devices are formed, fixing the wafer by adhering an adhesion sheet to the surface of the wafer on which semiconductor devices are formed and, then, grinding the back side of the wafer until reaching the groove to split into individual chips.
This method is effective for preventing the breakdown of thinned substrates because devices are split along dicing lines in a step of thinning. However, since the devices are perfectly split after thinning, all the devices can not be electrically connected in a step of back-metal plating to reinforce the substrate and, consequently, it is impossible to plate the whole surface of the wafer simultaneously. Thus, this method exhibits a very poor productivity.
Accordingly, an object of the present invention is to provide a method for manufacturing a device, which comprises a series of processes from a step of thinning a semiconductor device substrate having a large diameter, a step of reinforcing the thinned substrate, and a step of mounting the thinned device. More specifically, an object of the present invention is to provide a high-productive method of manufacturing a semiconductor device without damaging and polluting the semiconductor device substrate having a large diameter.
The method for manufacturing a semiconductor device substrate of the present invention is characterized by carrying out a series of processes from a step of uniformly thinning a whole surface of a semiconductor device substrate to a step of back-metal plating, while the semiconductor device substrate is unified with a dummy substrate. Therefore, the present invention allows a semiconductor device to be manufactured without breaking the thinned semiconductor device substrate even after the thinned substrate is separated from the dummy substrate.
First, the whole process of the present method for manufacturing a semiconductor device will be explained hereinafter.
A semiconductor device is bonded to a dummy substrate by using an adhesive sheet and the like to unify them. After the unified substrates are fixed on a pedestal support with wax and the like, the semiconductor device substrate is thinned by mirror-polishing. The unified substrates are fixed by vacuuming, and the semiconductor device substrate is thinned by grinding or by etching the backside of the semiconductor device substrate. After thinning, a step of back-metal plating is carried out in the unified state of the thinned semiconductor device substrate/the dummy substrate. Subsequently, the thinned substrate that has been plated is separated from the dummy substrate. After separation, the thinned substrate that has been plated is diced.
Particularly, in the case of polishing or grinding, an intrasubstrate fluctuation in the thickness of the dummy substrate to which the semiconductor device substrate is bonded with the adhesive sheet, is finally reflected in an intrasubstrate fluctuation in the thickness of the thinned GaAs semiconductor device substrate. Therefore, it is especially required that the intrasubstrate fluctuation in the thickness of the dummy substrate is small.
For example, when it is desired that a semiconductor substrate is thinned to 30 &mgr;m, if the fluctuation within a surface in the thickness of the dummy substrate is 10 &mgr;m, the thickness of the thinned semiconductor substrate becomes 20~40 &mgr;m (30±10 &mgr;m), resulting in that the thickness of the substrate within the surface varies twice at maximum. Considering that the thermal resistance of a semiconductor substrate is approximately proportional to the thickness of the substrate, the thermal resistance of the substrate within the surface varies twice. That is, the fluctuation in the thickness of the dummy substrate results in the fluctuation in the thermal resistance of the device obtained after thinning and, in turn, it affects the reliability of the device.
Therefore, in the case of thinning a semiconductor device substrate to a thickness of 40 &mgr;m or less, it is desirable that the intrasubstrate fluctuation in the thickness of the dummy substrate is within ±5 &mgr;m.
Generally, when a substrate is thinned, in order to improve workability of thinning, an abrasive having a large particle size (e.g., particle size 9 &mgr;m) is used to grind the substrate to achieve a predetermined thickness in a short period. The maximum difference in the thickness within the uneven surface that has been thinned is 2 &mgr;m or more.
SUMMARY OF THE INVENTION
As will be explained later, the present inventors have found that when an Au plate layer was formed on a GaAs substrate, the maximum difference in the thickness within the uneven surface greatly affected an adherability between the GaAs substrate and the Au plate layer.
Generally, a back metal layer is formed on a substrate by dip-etching the substrate to clean its surface, depositing a power feed layer for plating on the surface and, thereafter, plating a metal. However, dip etching alone can not make the maximum difference in the thickness within the uneven surface below 0.5 &mgr;m, and the adherability of the plate layer is insuf
Birch & Stewart Kolasch & Birch, LLP
Niebling John F.
Roman Angel
Sharp Kabushiki Kaisha
LandOfFree
Method for manufacturing a semiconductor device having a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for manufacturing a semiconductor device having a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for manufacturing a semiconductor device having a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3178119